1. Field of the Invention
The present invention relates to a power storage system for efficiently storing electric power such as surplus electric power produced at night or the like.
2. Description of the Prior Art
An electric power storage system is known in which surplus electric power produced at night is discharged during the day to accommodate for peak loads and thereby effectively utilize the power in the case where a difference in power consumption during the day and at night is remarkably large. The most representative one of these system is a pumped storage power station in which water is pumped up to a dam at night and electric power is generated by means of a hydraulic turbine generator during a period of the day when power consumption is large.
A pumped storage power station is constructed in a mountainous region by building a dam; hence, its location is limited, and the period of its construction is also long. Therefore, it cannot be used to respond quickly to the rapidly increasing demand for electric power in the case where there is a difference in power consumption during the day and at night. In addition, the efficiency of a pumped storage power station is about 60-70%. Therefore, a power storage system having a higher storage efficiency has been desired.